Enable gamma-correction on a face-by-face basis

Changes how we control if gamma-correction is done, and enables it for
the freetype CFF engine when stem-darkening is available.

The new code replaces existing hacks to force gamma-correction off
when using Freetype on X11 and Windows.

Change-Id: Ic703ca6965a3d81b204349e10f406c991b292edd
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

6 files changed, 27 insertions, 28 deletions

diff --git a/src/gui/painting/qdrawhelper.cpp b/src/gui/painting/qdrawhelper.cpp
index 8a9f8b8bdc..6f82ab871c 100644
--- a/src/gui/painting/qdrawhelper.cpp
+++ b/src/gui/painting/qdrawhelper.cpp
@@ -5547,7 +5547,7 @@ static void qt_alphamapblit_quint16(QRasterBuffer *rasterBuffer,
                                     int x, int y, const QRgba64 &color,
                                     const uchar *map,
                                     int mapWidth, int mapHeight, int mapStride,
-                                    const QClipData *)
+                                    const QClipData *, bool /*useGammaCorrection*/)
 {
     const quint16 c = color.toRgb16();
     quint16 *dest = reinterpret_cast<quint16*>(rasterBuffer->scanLine(y)) + x;
@@ -5572,18 +5572,16 @@ static void qt_alphamapblit_quint16(QRasterBuffer *rasterBuffer,
     }
 }
 
-static inline void rgbBlendPixel(quint32 *dst, int coverage, QRgba64 slinear, const QColorProfile *colorProfile)
+static inline void rgbBlendPixel(quint32 *dst, int coverage, QRgba64 slinear, const QColorProfile *colorProfile, bool useGammaCorrection)
 {
     // Do a gammacorrected RGB alphablend...
-    const QRgba64 dlinear = colorProfile->toLinear64(*dst);
+    const QRgba64 dlinear = useGammaCorrection ? colorProfile->toLinear64(*dst) : QRgba64::fromArgb32(*dst);
 
     QRgba64 blend = rgbBlend(dlinear, slinear, coverage);
 
-    *dst = colorProfile->fromLinear64(blend);
+    *dst = useGammaCorrection ? colorProfile->fromLinear64(blend) : toArgb32(blend);
 }
 
-Q_GUI_EXPORT bool qt_needs_a8_gamma_correction = false;
-
 static inline void grayBlendPixel(quint32 *dst, int coverage, QRgba64 slinear, const QColorProfile *colorProfile)
 {
     // Do a gammacorrected gray alphablend...
@@ -5598,7 +5596,7 @@ static void qt_alphamapblit_uint32(QRasterBuffer *rasterBuffer,
                                    int x, int y, quint32 color,
                                    const uchar *map,
                                    int mapWidth, int mapHeight, int mapStride,
-                                   const QClipData *clip)
+                                   const QClipData *clip, bool useGammaCorrection)
 {
     const quint32 c = color;
     const int destStride = rasterBuffer->bytesPerLine() / sizeof(quint32);
@@ -5610,7 +5608,7 @@ static void qt_alphamapblit_uint32(QRasterBuffer *rasterBuffer,
     const QRgba64 slinear = colorProfile->toLinear64(c);
 
     bool opaque_src = (qAlpha(color) == 255);
-    bool doGrayBlendPixel = opaque_src && qt_needs_a8_gamma_correction;
+    bool doGrayBlendPixel = opaque_src && useGammaCorrection;
 
     if (!clip) {
         quint32 *dest = reinterpret_cast<quint32*>(rasterBuffer->scanLine(y)) + x;
@@ -5680,9 +5678,9 @@ static void qt_alphamapblit_argb32(QRasterBuffer *rasterBuffer,
                                    int x, int y, const QRgba64 &color,
                                    const uchar *map,
                                    int mapWidth, int mapHeight, int mapStride,
-                                   const QClipData *clip)
+                                   const QClipData *clip, bool useGammaCorrection)
 {
-    qt_alphamapblit_uint32(rasterBuffer, x, y, color.toArgb32(), map, mapWidth, mapHeight, mapStride, clip);
+    qt_alphamapblit_uint32(rasterBuffer, x, y, color.toArgb32(), map, mapWidth, mapHeight, mapStride, clip, useGammaCorrection);
 }
 
 #if Q_BYTE_ORDER == Q_LITTLE_ENDIAN
@@ -5690,9 +5688,9 @@ static void qt_alphamapblit_rgba8888(QRasterBuffer *rasterBuffer,
                                      int x, int y, const QRgba64 &color,
                                      const uchar *map,
                                      int mapWidth, int mapHeight, int mapStride,
-                                     const QClipData *clip)
+                                     const QClipData *clip, bool useGammaCorrection)
 {
-    qt_alphamapblit_uint32(rasterBuffer, x, y, ARGB2RGBA(color.toArgb32()), map, mapWidth, mapHeight, mapStride, clip);
+    qt_alphamapblit_uint32(rasterBuffer, x, y, ARGB2RGBA(color.toArgb32()), map, mapWidth, mapHeight, mapStride, clip, useGammaCorrection);
 }
 #endif
 
@@ -5704,7 +5702,7 @@ inline static int qRgbAvg(QRgb rgb)
 static void qt_alphargbblit_argb32(QRasterBuffer *rasterBuffer,
                                    int x, int y, const QRgba64 &color,
                                    const uint *src, int mapWidth, int mapHeight, int srcStride,
-                                   const QClipData *clip)
+                                   const QClipData *clip, bool useGammaCorrection)
 {
     const quint32 c = color.toArgb32();
 
@@ -5714,7 +5712,7 @@ static void qt_alphargbblit_argb32(QRasterBuffer *rasterBuffer,
     if (!colorProfile)
         return;
 
-    const QRgba64 slinear = colorProfile->toLinear64(c);
+    const QRgba64 slinear = useGammaCorrection ? colorProfile->toLinear64(c) : color;
 
     if (sa == 0)
         return;
@@ -5729,7 +5727,7 @@ static void qt_alphargbblit_argb32(QRasterBuffer *rasterBuffer,
                     dst[i] = c;
                 } else if (coverage != 0xff000000) {
                     if (dst[i] >= 0xff000000) {
-                        rgbBlendPixel(dst+i, coverage, slinear, colorProfile);
+                        rgbBlendPixel(dst+i, coverage, slinear, colorProfile, useGammaCorrection);
                     } else {
                         // Give up and do a naive blend.
                         const int a = qRgbAvg(coverage);
@@ -5765,7 +5763,7 @@ static void qt_alphargbblit_argb32(QRasterBuffer *rasterBuffer,
                         dst[xp] = c;
                     } else if (coverage != 0xff000000) {
                         if (dst[xp] >= 0xff000000) {
-                            rgbBlendPixel(dst+xp, coverage, slinear, colorProfile);
+                            rgbBlendPixel(dst+xp, coverage, slinear, colorProfile, useGammaCorrection);
                         } else {
                             // Give up and do a naive blend.
                             const int a = qRgbAvg(coverage);
diff --git a/src/gui/painting/qdrawhelper_neon.cpp b/src/gui/painting/qdrawhelper_neon.cpp
index a833520b00..cdb374f823 100644
--- a/src/gui/painting/qdrawhelper_neon.cpp
+++ b/src/gui/painting/qdrawhelper_neon.cpp
@@ -539,7 +539,7 @@ void qt_alphamapblit_quint16_neon(QRasterBuffer *rasterBuffer,
                                   int x, int y, const QRgba64 &color,
                                   const uchar *bitmap,
                                   int mapWidth, int mapHeight, int mapStride,
-                                  const QClipData *)
+                                  const QClipData *, bool /*useGammaCorrection*/)
 {
     quint16 *dest = reinterpret_cast<quint16*>(rasterBuffer->scanLine(y)) + x;
     const int destStride = rasterBuffer->bytesPerLine() / sizeof(quint16);
diff --git a/src/gui/painting/qdrawhelper_neon_p.h b/src/gui/painting/qdrawhelper_neon_p.h
index 3cf949fc32..40475a9bde 100644
--- a/src/gui/painting/qdrawhelper_neon_p.h
+++ b/src/gui/painting/qdrawhelper_neon_p.h
@@ -91,7 +91,7 @@ void qt_alphamapblit_quint16_neon(QRasterBuffer *rasterBuffer,
                                   int x, int y, const QRgba64 &color,
                                   const uchar *bitmap,
                                   int mapWidth, int mapHeight, int mapStride,
-                                  const QClipData *clip);
+                                  const QClipData *clip, bool /*useGammaCorrection*/);
 
 void qt_scale_image_argb32_on_rgb16_neon(uchar *destPixels, int dbpl,
                                          const uchar *srcPixels, int sbpl, int srch,
diff --git a/src/gui/painting/qdrawhelper_p.h b/src/gui/painting/qdrawhelper_p.h
index 933da56095..f35b763f93 100644
--- a/src/gui/painting/qdrawhelper_p.h
+++ b/src/gui/painting/qdrawhelper_p.h
@@ -111,13 +111,13 @@ typedef void (*AlphamapBlitFunc)(QRasterBuffer *rasterBuffer,
                                  int x, int y, const QRgba64 &color,
                                  const uchar *bitmap,
                                  int mapWidth, int mapHeight, int mapStride,
-                                 const QClipData *clip);
+                                 const QClipData *clip, bool useGammaCorrection);
 
 typedef void (*AlphaRGBBlitFunc)(QRasterBuffer *rasterBuffer,
                                  int x, int y, const QRgba64 &color,
                                  const uint *rgbmask,
                                  int mapWidth, int mapHeight, int mapStride,
-                                 const QClipData *clip);
+                                 const QClipData *clip, bool useGammaCorrection);
 
 typedef void (*RectFillFunc)(QRasterBuffer *rasterBuffer,
                              int x, int y, int width, int height,
diff --git a/src/gui/painting/qpaintengine_raster.cpp b/src/gui/painting/qpaintengine_raster.cpp
index 647bd5cb2c..68b8d78ac6 100644
--- a/src/gui/painting/qpaintengine_raster.cpp
+++ b/src/gui/painting/qpaintengine_raster.cpp
@@ -2555,7 +2555,7 @@ QRasterBuffer *QRasterPaintEngine::rasterBuffer()
 /*!
     \internal
 */
-void QRasterPaintEngine::alphaPenBlt(const void* src, int bpl, int depth, int rx,int ry,int w,int h)
+void QRasterPaintEngine::alphaPenBlt(const void* src, int bpl, int depth, int rx,int ry,int w,int h, bool useGammaCorrection)
 {
     Q_D(QRasterPaintEngine);
     QRasterPaintEngineState *s = state();
@@ -2610,14 +2610,14 @@ void QRasterPaintEngine::alphaPenBlt(const void* src, int bpl, int depth, int rx
             } else if (depth == 8) {
                 if (s->penData.alphamapBlit) {
                     s->penData.alphamapBlit(rb, rx, ry, s->penData.solid.color,
-                                            scanline, w, h, bpl, 0);
+                                            scanline, w, h, bpl, 0, useGammaCorrection);
                     return;
                 }
             } else if (depth == 32) {
                 // (A)RGB Alpha mask where the alpha component is not used.
                 if (s->penData.alphaRGBBlit) {
                     s->penData.alphaRGBBlit(rb, rx, ry, s->penData.solid.color,
-                                            (const uint *) scanline, w, h, bpl / 4, 0);
+                                            (const uint *) scanline, w, h, bpl / 4, 0, useGammaCorrection);
                     return;
                 }
             }
@@ -2646,10 +2646,10 @@ void QRasterPaintEngine::alphaPenBlt(const void* src, int bpl, int depth, int rx
             }
             if (depth == 8)
                 s->penData.alphamapBlit(rb, rx, ry, s->penData.solid.color,
-                                        scanline, w, h, bpl, clip);
+                                        scanline, w, h, bpl, clip, useGammaCorrection);
             else if (depth == 32)
                 s->penData.alphaRGBBlit(rb, rx, ry, s->penData.solid.color,
-                                        (const uint *) scanline, w, h, bpl / 4, clip);
+                                        (const uint *) scanline, w, h, bpl / 4, clip, useGammaCorrection);
             return;
         }
     }
@@ -2807,7 +2807,8 @@ bool QRasterPaintEngine::drawCachedGlyphs(int numGlyphs, const glyph_t *glyphs,
             alphaPenBlt(alphaMap->constBits(), alphaMap->bytesPerLine(), alphaMap->depth(),
                         qFloor(positions[i].x) + offset.x(),
                         qRound(positions[i].y) + offset.y(),
-                        alphaMap->width(), alphaMap->height());
+                        alphaMap->width(), alphaMap->height(),
+                        fontEngine->expectsGammaCorrectedBlending());
 
             fontEngine->unlockAlphaMapForGlyph();
         }
@@ -2868,7 +2869,7 @@ bool QRasterPaintEngine::drawCachedGlyphs(int numGlyphs, const glyph_t *glyphs,
                 drawImage(QPoint(x, y), QImage(glyphBits, c.w, c.h, bpl, image.format()));
                 s->matrix = originalTransform;
             } else {
-                alphaPenBlt(glyphBits, bpl, depth, x, y, c.w, c.h);
+                alphaPenBlt(glyphBits, bpl, depth, x, y, c.w, c.h, fontEngine->expectsGammaCorrectedBlending());
             }
         }
     }
diff --git a/src/gui/painting/qpaintengine_raster_p.h b/src/gui/painting/qpaintengine_raster_p.h
index 59213220a6..d0b82b3a93 100644
--- a/src/gui/painting/qpaintengine_raster_p.h
+++ b/src/gui/painting/qpaintengine_raster_p.h
@@ -225,7 +225,7 @@ public:
 #endif
 
     QRasterBuffer *rasterBuffer();
-    void alphaPenBlt(const void* src, int bpl, int depth, int rx,int ry,int w,int h);
+    void alphaPenBlt(const void* src, int bpl, int depth, int rx,int ry,int w,int h, bool useGammaCorrection);
 
     Type type() const Q_DECL_OVERRIDE { return Raster; }